Due to the flexibility of the materials used, flexible electronics produced using organic semiconductors can be fit to the outer surfaces or insides of the human body. Consequently, the use of flexible electronics to obtain biological information directly from cells or tissues has been garnering much attention in recent years.
Pressure sensors are attracting attention as one such application. A pressure sensor is a device that outputs an applied pressure as an electrical signal. Pressure sensors are widely used, for example, in artificial skin and robot operations and the like (Patent Document 1). These technologies continue to develop rapidly, and more precise data is now being demanded. In order to obtain more precise data, it is necessary for the pressure sensor to better fit the shape of the object being measured, and for the pressure sensor to be capable of better following movements such as bending and extending. Accordingly, thinner and more flexible pressure sensors are required.
In order to realize such pressure sensors, the types of investigations described below are being pursued.
Patent Document 2 discloses, as a simple matrix pressure-sensitive sensor, a pressure-sensitive sheet obtained by vertically and horizontally weaving a pressure-sensitive wire composed of a cylindrical elastic body, a conductive layer formed as a layer on the outer peripheral surface of the cylindrical elastic body, and a dielectric layer formed on top of the conductive layer.
Patent Document 3 discloses an active matrix pressure-sensitive sensor that uses electrodes, a pressure-sensitive conductive sheet and a transistor, and also discloses a pressure-sensitive conductive sheet in which graphite is added to a silicon rubber.
Patent Document 4 discloses a flexible pressure-sensitive sensor having a structure containing two or more layers, the sensor including a pressure-sensitive conductive sheet prepared by forming a resin coating film containing a conductive material on the surface of a rubber substrate. By using a structure containing two or more layers, the hysteresis of changes in the pressure-resistance can be improved.